Bush, Obama meet at White House
Mr Bush, a Republican, and Mr Obama, a Democrat, met privately for about 30 minutes ahead of the wider gathering and were expected to discuss the US economy and the crisis in the Middle East.
Then former presidents Jimmy Carter and Bill Clinton, both Democrats, and Republican George HW Bush, the current president's father, met Mr Bush and Mr Obama in the Oval Office for a photo session with journalists.
"I want to thank the president-elect for joining the ex-presidents for lunch," the younger Mr Bush told Mr Obama, who stood next to him, nodding.
"One message that I have and I think we all share is that we want you to succeed. Whether we're Democrat or Republican, we care deeply about this country," Mr Bush continued.
The five men, all standing in a line in front of the president's desk, smiled and rubbed shoulders, with Mr Carter standing somewhat more to the side of the group.
The senior Mr Bush stood next to Mr Obama, with the current president next, followed by Mr Clinton and Mr Carter.
"All of us who have served in this office understand that the office itself transcends the individual and we wish you all the very best, and so does the country," Mr Bush said to his successor. "To the extent we can, we look forward to sharing our experiences with you."
Mr Obama called the gathering extraordinary and thanked the current president for hosting it.
"All the gentlemen here understand both the pressures and possibilities of this office, and for me to have the opportunity to get advice, good counsel and fellowship with these individuals is extraordinary," he said.
When asked by a reporter what he learned from the other four men's mistakes, Mr Obama retorted: "From their successes!"
Despite last year's heated political campaign when Obama attacked Bush regularly over foreign and domestic policy, the transition process between the November 4th election and Mr Obama's January 20th inauguration has proceeded smoothly.
Though they have much in common, relations between the different presidents have not always been rosy.
Mr Carter has criticised Mr Bush's presidency as "the worst in history" with regard to international relationships and Mr Clinton, who has a warm relationship with the senior Mr Bush, criticised the current president and Mr Obama sharply during his wife Hillary Clinton's White House bid last year.
Today's event was the first such gathering of former US heads of state at the White House in 27 years. After their meeting in the Oval Office, the five men were to have lunch in a chandeliered private dining room.